To a certain extent, the present invention was inspired by attempting to solve the problem of drilling multiple holes in printed circuit boards which, even in small sizes, frequently have a very substantial number of holes of varying diameters drilled in precise patterns therein for purposes of receiving connecting pins, contacts or wires on various electrical components which are integrally fixed to the printed circuit on the board by soldering. Drilling such a multiplicity of holes has heretofore been a very time-consuming operation, the crudest methods comprising individually drilling said holes by a single drill mounted either in a drill press or a numerical control or drilling machine. The close relationship of said holes renders the drilling thereof by automatic means very difficult in view of the need to simultaneously operate a plurality of drills in a precise pattern without conflict between the various drills which must be powered, and the frequent changing of drill bits to accommodate the plurality of diameters usually required.
It has been the practice in certain manufacturing operations to operate a multiplicity of drills by various power means where the close proximity of the holes drilled thereby is not as acute as found in the drilling of holes in printed circuit boards. For example, in drilling spaced holes in ladder rails for receiving the ends of the rungs of the ladder by means of a gang of drills is well-known and providing power means to operate such drills simultaneously is readily solved by gear trains, chains, or otherwise. Further, gang drilling machines which have adjustable mounts for the drills to accommodate the same to different patterns also are known, and examples of these are included among the following patents, which are typical of mechanically-operated drilling machines in which the drills are operated by gears or otherwise, as referred to above:
______________________________________ U.S. Pat. No. 2,215,273 Paradis Sept. 17, 1940 U.S. Pat. No. 3,635,570 DeGelleke et al Jan. 18, 1972 U.S. Pat. No. 3,765,787 Hart et al Oct. 16, 1973 U.S. Pat. No. 3,822,958 Lewis July 9, 1974 U.S. Pat. No. 4,090,803 Haley May 23, 1978 ______________________________________
Another problem existing in the operation of gang drills comprises detecting either malfunctioning individual drills or broken drill bits, especially when mass production is involved, and efforts have been made heretofore to provide various types of detecting means for such broken bits or malfunctioning power means, and typical examples of such devices are illustrated in the following patents:
______________________________________ U.S. Pat. No. 3,025,728 Cross et al Mar. 20, 1962 U.S. Pat. No. 3,310,796 Sanders Mar. 21, 1967 U.S. Pat. No. 3,381,550 Smith May 7, 1968 U.S. Pat. No. 3,627,437 Smith Dec. 14, 1941 U.S. Pat. No. 3,669,557 Mitchell June 13, 1972 U.S. Pat. No. 3,747,085 Bala et al July 17, 1973 ______________________________________
Forming a support means for a multiplicity of drills also has been a problem requiring attention heretofore but especially where the proximity of the holes to be drilled isn't acute, compared to drilling of holes in printed circuit boards, it has not been particularly difficult to devise supports and mounting means for a plurality of drill shanks or chucks, but especially where drill holes are in very close proximity, as in printed circuit boards, some means for forming a support for a plurality of preferably small size power heads has given rise to the investigation of employing different materials and methods for forming such support means and investigations of suitable solutions for providing such support means comprises the subject matter of the present invention. In this, as described in greater detail hereinafter, the basic support panel is formed from a pourable and settable slurry of material having high fracture strength and in regard to investigating certain features of the invention, the most pertinent prior activities which have been found comprise prior U.S. Pat. No. 3,108,329 to Chapman, dated Oct. 29, 1963 and U.S. Pat. No. 3,290,421 to Miller, Jr., dated Dec. 6, 1966, and the distinction of the present invention over the subject matter of these patents is set forth hereinbelow.